The present invention relates to electrical grounding devices and, more particularly, to an universal clamp used in coupling rods, pipes or other structures of various cross-sections to ground mechanisms.
In many instances, there is a need to provide an electrical coupling to structures of various sized and shaped cross-sections for grounding purposes. These instances include grounding of pipes, conduit, and other structures of mechanical and/or electrical systems to dissipate electrical charge to protect the systems and/or individuals who may come in contact with the components of such systems. Grounding clamps are commonly employed for these purposes.
Grounding clamps come in a variety of configurations and use various means for forming a conductive attachment. One type of clamp includes a metal strap with a plurality of holes, a metal stud, and conventional nuts to secure the strap about the periphery of the structure. More specifically, the metal strap encircles the structure and the threaded stud is inserted through two of the holes to secure the metal strap tightly around the periphery of the structure. The metal strap is drawn tightly around the periphery of the structure as the nut is tightened on the bolt. The clamp typically includes a ground terminal to which a wire is attached for connecting the clamp to a conventional ground mechanism, such as a ground rod. Strap type clamps accommodate different diameters of pipes or conduits or cross-sections of other shaped structures, such as boxes. This adaptability to a variety of structures eliminates the need for an inventory of grounding clamps that are specifically designed for a specified structure.
Strap-type clamps typically use nuts with sharp edges. These sharp edges are known to gouge the metal strap as the metal strap is tightened at the stud. This gouging causes creases and areas of weakness which severely shortens the overall life of the strap and can limit the effectiveness with which it conducts electricity.
One solution to gouging, or otherwise providing a non-destructive tightening of the strap, is disclosed in my U.S. Pat. No. 4,626,051, which discloses the use of two nuts, each having a smooth curved surface for engaging the strap. The curvature of the surface better accepts the angle of the metal strap as it leaves the various structures and attaches to the stud. While this advancement successfully prevents the gouging of the strap by eliminating the sharp edges of the engagement, one of the nuts must be removed from the stud during installation, and this leads to the possibility of losing the nut and/or lost time retrieving (if even possible) the lost nut. This situation is compounded by the fact that many installations are made in awkward and sometimes dangerous locations, such as those to suspended systems requiring installers to use scaffolding, catwalks and/or ladders to reach the suspended structures.
Thus, the present invention addresses the need for an entirely self contained universal clamp that eliminates loose parts.
The present invention relates to a universal ground clamp for structures with different cross-sectional shape. The clamp includes an elongated strap that is capable of extending around a structure. The strap defines at least two holes and has least one end stop. A securing stud is able to extend through at least two of the holes when the strap is encircled around a structure to tighten the strap. A first strap engaging plate is supported on the securing stud and has a curved surface to engage the strap with a smooth transition. A second strap engaging plate is slidingly supported on the strap and is maintained on the strap by at least one end stop of the strap. The second strap engaging plate has a curved surface to engage the strap with a smooth transition is configured to cooperate with the stud to tighten the clamp between the curved surface of the first strap engaging plate and the curved surface of the second strap engaging plate. A terminal ground wire attachment is provided on the securing stud.
The second strap engaging plate may define a slot through which the strap extends. The second securing plate may include a straight portion that includes the slot though which the strap extends. The second securing plate also may include a second curved portion to locate the slot of the straight portion so that the strap extends over the first curved portion.
The securing stud may include a threaded portion. Further, the second strap engaging plate may define an internally threaded bore that cooperates with the threaded portion of the securing stud to tighten the strap about a structure. The second securing plate also may include a curved portion that includes the curved surface that engages the strap and defines the internally threaded bore.
The at least one stop may be formed integral with the end of the strap. The at least one stop also may be formed from a portion of the strap being deformed to extend out of the plane of the strap.
The terminal ground wire attachment may be clamp. The terminal ground wire clamp may further include a first hole defined by the stud, a second hole defined by the stud that intersects the first hole, and a stud that inserts into the second hole to provide a clamping effect in the first hole.